A TIMESCALE FOR SEX VERSUS PARTHENOGENESIS - EVIDENCE FROM SUBFOSSIL OSTRACODS

Parthenogenetic and sexual reproduction co-occur in many animals. In s uch groups, determination of the timescale over which parthenogenetic lineages can persist and provide an advantage over sexual reproduction is of considerable importance, as the adoption of either reproductive mode will confer various, but conflicting, adaptational advantages. D ata derived from a survey of ostracod valves preserved in 34 Holocene freshwater sediment cores suggest that environmental fluctuations duri ng a period of less than 5000 years were sufficient to provide an adva ntage to sexually reproducing ostracods over parthenogenetic forms. In addition, asexual species were found not to have colonized water bodi es earlier than sexual forms, nor to have persisted for longer. When v iewed over timescales such as these, subfossil Ostracoda offer little support for the 'general purpose genotype' hypothesis of parthenogenes is, and also suggest that the short-term costs of sexual reproduction are rapidly outweighed by its advantages in a changing environment.